Half-float attribute support

[simon-paris]

Description of the problem

It's currently impossible to make a half float attributes work, since the GL buffer type is derived from the JS buffer type, and JS doesn't have a half float buffer type.

I'd like to add a special case to Uint16 and Int16 attributes that causes them to be interpreted as half floats.

var myAttr = new THREE.BufferAttribute(new Uint16Array(whatever), 3);
myAttr.useHalfFloat = true;

Would this be acceptable?

Three.js version

• All

Browser

• All of them

OS

• All of them

[Mugen87]

I personally would love to see Float16Array 😇

https://esdiscuss.org/topic/float16array

Without such a data type, you have to manually perform the conversion to half-float which is cumbersome. I'm not sure we want code like the following in the library core:

http://codeflow.org/experiment/half-float/main.js

[mrdoob]

Could be a good idea to start with a example though.

If I understand correctly, what we need in core is a way to hint the renderer that we attribute is half-float and then a helper (in examples) to convert the array. Correct?

[Mugen87]

I think so. @simon-paris Do you want to give it a try?

BTW: I have create a test fiddle for the forum some time ago that shows how to use a data texture with half float data (THREE.HalfFloatType):

https://jsfiddle.net/f2Lommf5/1856/

It would be great if the helper could also be used to convert the data for this use case. Right now, I manually set the half float value for 10000.

[WestLangley]

https://github.com/mrdoob/three.js/blob/dev/examples/js/loaders/HDRCubeTextureLoader.js#L27

[Mugen87]

How convenient^^

[mrdoob]

https://github.com/mrdoob/three.js/blob/dev/examples/js/loaders/HDRCubeTextureLoader.js#L27

We may want to add that code in core then, so we can do it at upload time and it all works nicely?

[Mugen87]

Okay. But one thing bothers me. BufferAttribute.useHalfFloat would only work in specific cases (when using Uint16Array and Int16Array). I think it's better to put the property to Int16BufferAttribute and Uint16BufferAttribute.

[mrdoob]

So rather than adding useHalfFloat you are suggesting we check for attribute.isFloat16BufferAttribute instead?

[Mugen87]

I've meant we should not introduce a new property to BufferAttribute. I would add a property to the more specific classes Int16BufferAttribute and Uint16BufferAttribute. Another option might be to introduce Float16BufferAttribute...

[Mugen87]

Um, it seems that WebGLRenderingContext.vertexAttribPointer() accepts half float attributes only with WebGL 2, see

https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/vertexAttribPointer